Reverse burn power charge for a wellbore tool

ABSTRACT

A power charge and method for actuating a wellbore tool with a power charge. The power charge may include a groove formed in the outer surface of the power charge. The power charge may include a first volume containing a first energetic material and a second volume containing a second energetic material that is a faster burning material compared to the first energetic material. The wellbore tool may include a tool body wall defining a power charge cavity. The groove formed in the outer surface of the power charge may define a gas pressure path between the tool body wall and the power charge, within the power charge cavity, when the power charge is inserted into the power charge cavity. The method may include coupling an initiator to the wellbore tool and initiating combustion of the first energetic material and the second energetic material to actuate the wellbore tool.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/886,257 filed May 28, 2020, which claims the benefit of U.S.Provisional Patent Application No. 62/853,824 filed May 29, 2019, theentire contents of which are incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

Oil and gas are extracted by subterranean drilling and introduction oftools into the resultant wellbore for performing various functions. Thework performed by tools introduced in a wellbore may be achieved by aforce exerted by expanding gases; the expanding gases may be the resultof combustion of an energetic material.

One example of a wellbore tool is a setting tool. Among other functions,a setting tool is utilized to place plugs at locations inside thewellbore to seal portions of the wellbore from other portions. The forceexerted to set a plug is typically exerted on a piston in the settingtool, with the piston acting to deform or displace portions of the plugwhich then engage the walls of the wellbore. The engagement of thewellbore wall by the deformed portions of the plug hold the plug, aswell as any elements attached to the plug, stationary in the wellbore.The plug and any associated elements may completely or partially sealthe wellbore, and the associated elements may function to vary thiscomplete/partial blockage depending upon circumstances.

Primarily used during completion or well intervention, a plug maypressure isolate a part of the wellbore from another part. For example,when work is carried out on an upper section of the well, the lower partof the wellbore must be isolated and plugged; this is referred to aszonal isolation. Plugs can be temporary or permanent. Temporary plugscan be retrieved whereas permanent plugs can only be removed bydestroying them with a drill. There are number of types of plugs, e.g.,bridge plugs, cement plugs, frac plugs and disappearing plugs. Plugs maybe set using a wire-line, coiled tubing, drill pipe or untethereddrones. In a typical operation, a plug can be disposed into a well andpositioned at a desired location in the wellbore. A setting tool may beattached to and lowered along with the plug or it may be lowered afterthe plug, into an operative association therewith.

The expanding gases in a tool typically result from a chemical reactioninvolving a power charge. In the example of a setting tool, activationof the chemical reaction in the power charge results in a substantialforce being exerted on the setting tool piston. When it is desired toset the plug, the self-sustaining chemical reaction in the power chargeis initiated, resulting in expanding gas exerting a substantial force onthe piston. The piston being constrained to movement in a singledirection, the substantial force causes the piston to move axially andactuate the plug to seal a desired area of the well. The substantialforce exerted by the power charge on the piston can also shear one ormore shear pins or similar frangible members that serve certainfunctions, e.g., holding the piston in place prior to activation andseparating the setting tool from the plug.

The force applied to a tool by the power charge must be controlled; itmust be sufficient to actuate the tool reliably but not so excessive asto damage the downhole tools or the wellbore itself. Also, even a verystrong force can fail to properly actuate a tool if delivered tooabruptly or over too short a time duration. Even if a strong force overa short time duration will actuate a tool, such a set-up is not ideal.That is, a power charge configured to provide force over a period of afew seconds or tens of seconds instead of a few milliseconds issometimes required and the desired option. In the context of a settingtool, such an actuation is referred to as a “slow set”. Depending on theparticular function of a given tool and other parameters, favorableforce characteristics may be provided by a force achieving work over aperiod of milliseconds, several seconds or even longer.

FIG. 1 shows a power charge 116 contained in a prior art genericwellbore tool 60. A chemical reaction in power charge 116 results inexpanding gas exerting a force 86 on a piston 80 or other forcetransferring element. The piston 80, in turn, exerts an actuation force84 to accomplish a function of the generic tool 60. Initiation of thechemical reaction, e.g., combustion, begins at a section of power charge116 remote from piston 80 and the chemical reaction proceeds in adirection 88 toward piston 80. A problem in the prior art is that theportion of the power charge 116 that has not undergone the chemicalreaction may block the expanding gas from exerting the force 86 onpiston 80. Thus, expanding gas pressure will increase until it is ableto exert a force on the piston 80 and begin moving the piston 80 toexert the actuation force 84 to achieve the function of the generic tool60.

In view of the disadvantages associated with currently available powercharges, there is a need for a safe, predictable and economical powercharge for use in wellbore tools. The improved power charge will reduceextraneous forces developed during the chemical reaction, i.e., amuch-improved force/time profile will be achieved. Such improvements mayresult in smaller power charges being required and reduced maximumforces within the tool; both of these results will reduce the likelihoodof inadvertent damage to the tool.

BRIEF DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In an aspect, the disclosure is directed to a power charge for actuatinga wellbore tool. An exemplary power charge has a first end and a secondend opposite the first end, and an outer surface extending from thefirst end to the second end. A groove is formed in the outer surface ofthe power charge. The power charge includes a first volume containing afirst energetic material and a second volume containing a secondenergetic material. The second energetic material is a faster burningmaterial compared to the first energetic material.

In another aspect, the disclosure is directed to a wellbore toolincluding a power charge for actuating the wellbore tool. An exemplarywellbore tool includes a tool body wall that defines a power chargecavity. The power charge is positioned within the power charge cavityand includes a first end and a second end opposite the first end, and anouter surface extending from the first end to the second end. A grooveis formed in the outer surface of the power charge. The power chargeincludes a first volume containing a first energetic material and asecond volume containing a second energetic material that is a fasterburning material compared to the first energetic material.

In another aspect, the disclosure is directed to a method for actuatinga wellbore tool with a power charge. An exemplary method includesproviding the wellbore tool including a power charge cavity defined by atool body wall of the wellbore tool, and inserting the power charge intothe power charge cavity. The exemplary power charge includes a first endand a second end opposite the first end, and an outer surface extendingfrom the first end to the second end. A groove is formed in the outersurface of the power charge and defines a gas pressure path between thetool body wall and the power charge, within the power charge cavity,when the power charge is inserted into the power charge cavity. Thepower charge includes a first volume containing a first energeticmaterial and a second volume containing a second energetic material thatis a faster burning material compared to the first energetic material.The method further includes coupling an initiator to the wellbore tool.Initiating the initiator initiates an ignition portion of the powercharge causing combustion of the first energetic material and the secondenergetic material and generation of gas pressure from combustion of thefirst energetic material and the second energetic material. The gaspressure travels along the gas pressure path and is used to actuate thewellbore tool.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description will be rendered by reference to specificexemplary embodiments thereof that are illustrated in the appendeddrawings. Understanding that these drawings depict only exemplaryembodiments thereof and are not therefore to be considered to belimiting of its scope, the exemplary embodiments will be described andexplained with additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 is a cross-sectional, side, plan view of a generic prior artwellbore tool that utilizes a power charge to perform work;

FIG. 2 is a one-quarter-sectional, side, perspective view of a settingtool in accordance with an exemplary embodiment;

FIG. 3 is a cross-sectional, side, plan view of a setting tool inaccordance with an exemplary embodiment;

FIG. 4 is a cross-sectional, side, plan view of a power charge inaccordance with an exemplary embodiment;

FIG. 5A is an end, plan view of the power charge power charge shown inFIG. 4 viewed from the perspective of line A-A;

FIG. 5B is a cross-sectional, plan view of the power charge shown inFIG. 4 taken at line B-B;

FIG. 5C is a cross-sectional, plan view of the power charge shown inFIG. 4 taken at line C-C;

FIG. 6 is a cross-sectional, side, plan view of a power charge inaccordance with an exemplary embodiment;

FIG. 7 is a cross-sectional, side, plan view of a portion of a settingtool in accordance with an exemplary embodiment; and

FIG. 8 is a side, perspective view of a power charge in accordance withan exemplary embodiment.

Various features, aspects, and advantages of the exemplary embodimentswill become more apparent from the following detailed description, alongwith the accompanying figures in which like numerals represent likecomponents throughout the figures and text. The various describedfeatures are not necessarily drawn to scale but are drawn to emphasizefeatures of the exemplary embodiments.

The headings used herein are for organizational purposes only and arenot meant to limit the scope of the description or the claims. Tofacilitate understanding, reference numerals have been used, wherepossible, to designate like elements common to the figures.

DETAILED DESCRIPTION

Reference will now be made in detail to various exemplary embodiments.Each example is provided by way of explanation and is not meant as alimitation and does not constitute a definition of all possibleembodiments.

In the description that follows, the terms “setting tool”, “mandrel”,“initiator”, “power charge”, “piston”, “bore”, “apertures” and/or“channels”; and other like terms are to be interpreted and definedgenerically to mean any and all of such elements without limitation ofindustry usage. Such terms used with respect to exemplary embodiments inthe drawings should not be understood to necessarily connote aparticular orientation of components during use.

As used herein, the term “cylinder” includes cylinders and prisms havinga base of any shape. In addition, collections of cylinders havingdifferent base shapes and sizes stacked together are also encompassed bythe term “cylinder”.

For purposes of illustrating features of the exemplary embodiments,examples will now be introduced and referenced throughout thedisclosure. Those skilled in the art will recognize that these examplesare illustrative and not limiting and are provided purely forexplanatory purposes. For example, the exemplary embodiments presentedin FIGS. 2 and 3 show the use of a power charge 116 in exemplary settingtools. Although shown in the context of a setting tool 100, the powercharge 116 presented herein may be utilized in any wellbore tool capableof being actuated by expanding gas from a chemical reaction, e.g.,combustion. U.S. patent application Ser. No. 16/858,041 filed Apr. 24,2020, which is commonly owned by DynaEnergetics Europe GmbH andincorporated herein by reference in its entirety, provides additionaldetails regarding setting tools.

FIG. 2 illustrates a perspective, partial quarter-sectional view of anexemplary setting tool 100 for actuating a tool 102 in a wellbore. Thesetting tool 100 includes an inner piston 104 having a proximal end 106and a distal end 108. An intermediate section of the inner piston 104has an annular wall 112 enclosing a cavity 114. The cavity 114 isconfigured to receive a power charge 116 therein. The power charge 116is not shown in cross section. Thus, only the external surface of powercharge 116 is shown in FIG. 2. An initiator 118 may be positionedproximate to the power charge 116. The initiator 118 is used to initiatecombustion of the power charge 116 to form a combustion gas pressureinside the cavity 114.

Another component of setting tool 100 is an outer sleeve 120 having apiston proximal end 122, a piston distal end 124, a body 110, and acentral bore 126. The outer sleeve 120 is configured to slideablyreceive the inner piston 104. A generally annular expansion chamber 128may be defined by a portion of the central bore 126 of the outer sleeve120 and a portion of the annular wall 112 of the inner piston 104. A gasdiverter channel 134 extends through the annular wall 112 of the innerpiston 104. The gas diverter channel 134 is configured to allow gaspressure communication between the cavity 114 containing power charge116 and the expansion chamber 128. Accordingly, in the circumstancewhere the combusting portion of the power charge 116 has an unimpededgas pressure path to channel 134, the combustion gas will pass throughthe gas diverter channel 134 and into the expansion chamber 128.Increasing amounts of gaseous combustion products from burning powercharge 116 will increase the pressure in the cavity 114, the gasdiverter channel 134 and the expansion chamber 128. Expansion chamber128 is so named because it is adapted to expand in volume as a result ofaxial movement of the outer sleeve 120 relative to the inner piston 104.The increasing gas pressure in the expansion chamber 128 will exert anaxial force on outer sleeve 120 and inner piston 104, resulting in theouter sleeve 120 sliding axially toward tool 102 and expansion chamber128 increasing in volume.

Referring again to FIG. 2, the initiator 118 is configured forpositioning in an initiator holder 138. Initiator 118 may be of the typedescribed in U.S. Pat. No. 9,605,937 issued Mar. 28, 2017, which iscommonly owned by DynaEnergetics Europe GmbH and incorporated herein byreference in its entirety, and comprise an initiator head 146 and aninitiator shell 136. The initiator shell 136 may contain an electroniccircuit board (not shown) and an element, e.g., a fuse head (not shown),capable of converting an electrical signal into an ignition, flame orpyrotechnical output. Initiator head 146 includes an electricallycontactable line-in portion 148 through which electrical signals may beconveyed to the electronic circuit board of initiator 118.

The initiator holder 138 may be configured for positioning the initiatorshell 136 adjacent the power charge 116 within the inner piston 104. Theinitiator 118 is positioned sufficiently close to power charge 116 suchthat ignition of the initiator 118 will initiate combustion of powercharge 116.

In accordance with an embodiment, power charge 116 occupies a volume ofa cylinder, typically an elongated cylinder having an initiation end 186and a distal end 184 with the volume 178 of the power charge 116 betweenthe initiation end 186 and the distal end 184. The initiation end 186includes an ignition portion 188 of the power charge 116, i.e., theplace where combustion of the power charge 116 is initiated. Combustionof the power charge 116 will proceed from the ignition portion 188through the volume of the power charge 178 in any direction whereunreacted energetic material is sufficiently close to reacting, i.e.,burning, energetic material. Therefore, combustion of the power charge116 will generally proceed from the initiation end 186 to the distal end184 of the power charge. The rate at which combustion will proceed inthe power charge 116 is discussed hereinbelow. The exothermic chemicalreaction, e.g., combustion or burning, in the power charge 116 resultsin replacement of the solid energetic material of the power chargevolume 178 with gas and a small amount of particulate residual material.Since the cavity 114 is sealed by sub 512 and bulkhead 514 (FIG. 3), ithas a fixed volume. Thus, the gas produced by the exothermic chemicalreaction results in increasing gas pressure within the cavity 114.

In current setting tool wellbore tools, a path does not initially existfor gas pressure from the combustion gas produced early in thecombustion of power charge 116 to reach the gas diverter channel 134. Atime delay occurs before such a gas pressure path is opened. Thepressure built up in the cavity 114 prior to a path to the gas diverterchannel 134 being opened is delivered in a single pulse of a short burstof high force. Thus, current setting tools often have problemsdelivering a “slow set”, i.e., a force over a period of seconds tominutes instead less than a second or, perhaps, less than severalseconds. Thus, the favorable force characteristics achievable with aslow set may be difficult or impossible to achieve with currentlyavailable wellbore tools.

The most commonly used energetic material, i.e., chemical reactantresulting in expanding gas, is black powder. Black powder, also known asgunpowder, is the earliest known chemical explosive and includes sulfur,charcoal and potassium nitrate (saltpeter, KNO₃). The sulfur andcharcoal act as fuels while the saltpeter is an oxidizer. Because of theamount of heat and gas volume that it generates when burned, blackpowder has been used as a propellant for about 1000 years in firearms,artillery, rockets, and fireworks, and as a blasting powder inquarrying, mining, and road building. Black powder is referred to as alow explosive because of its slow reaction rate relative to highexplosives and consequently low brisance. Low explosives deflagrate,i.e., burn, at subsonic speeds in contrast to a supersonic wavegenerated by the detonation of high explosives. Ignition of black powdergenerates gas. When generated in a closed and constant volume, theincreased amount of gas result in increased pressure in the closedvolume. The force of this increased pressure in a closed volume may beutilized to perform work.

There exist a number of ‘substitutes’ for black powder. Variousparameters may be reduced or enhanced in a black powder substitutes(“BPS”). For example, the sensitivity as an explosive may be reducedwhile the efficiency as a propellant may be increased. The first widelyused BPS was Pyrodex®. Pyrodex® will produce a greater amount of gas perunit mass than black powder but has a reduced sensitivity to ignition.Both of these parameters may be considered improvements over blackpowder. Triple Seven® and Black Mag3® are sulfurless BPS that burn morequickly and develop greater pressure.

Rate of burn for black powder and BPS is a notoriously difficultparameter to measure or on which to find accurate data. This is possiblybecause of the number of variables that can have an effect on the rateof burn, i.e., black powder and BPS will burn at different ratesdepending upon a number of factors. Regardless, pure black powder andBPS will usually have a burn rate on the order of about 0.3 to about 0.7feet per second (“ft/sec”) which may be converted to about 18 feet perminute to about 42 feet per minute (“ft/min”). Mixing black powder orBPS with additives that are not fuel or oxidizer components contributingto the chemical reaction, i.e., “inert” ingredients, will typically slowthe burn rate. Further, the higher the proportion of inert ingredientsto black powder or BPS, the slower the burn rate will be.

The burn rate of a mixture containing black powder or BPS may beadjusted from very near the burn rate of pure black powder or BPS, i.e.,by adding very little inert material, to very much slower, i.e., byadding a large proportion of inert material. Formulations for the powercharge 116 for use in a wellbore tool are known that have a burn rate onthe order of about 12 ft/min down to about 0.5 ft/min or even lower.Thus, a fast-burning portion of the power charge may contain 50 to 100%black powder or BPS and 0 to 50% potassium nitrate (KNO₃).

In an embodiment, a formulation for a slow-burning power charge maycontain about 6% by weight of black powder or BPS, sodium nitrate(NaNO₃) as fuel, wheat flour (C₆H₁₀O₅) as oxidizer and an epoxy resin asa binder. Varying the ratio of epoxy resin provides a means of varyingthe burn rate for the power charge 116. In addition, the selection ofepoxy resin may have an impact on the burn rate. In an embodiment, apower charge permitting a slow-set are formulated to produce burn ratesfrom about 3 ft/min to about 0.13 ft/min. The slow-burning portion ofthe power charge may contain 40 to 75% sodium nitrate (NaNO₃), 0 to 10%black powder or BPS, 15 to 45% wheat flour, and 10 to 30% epoxy.

Utilizing the 18 ft/min to 42 ft/min values for pure black powder or BPSand power charge formulations with values of 3 ft/min to about 0.13ft/min results in relative burn rates from about 6:1 to about 300:1. Inan embodiment, relative burn rates between a fast reacting energeticmaterial and a slow reacting energetic material between about 100:1 and300:1 are contemplated.

As stated previously, a problem with current wellbore tools is that apath does not initially exist for gas pressure from the combustion gasproduced early in the combustion of power charge 116 to reach the gasdiverter channel 134. Thus, regardless of the reaction rate of theenergetic material, a time delay occurs before the gas pressure is ableto exert a force where it is needed. Also, the pressure built up in thecavity 114 prior to a path to the gas diverter channel 134 being openedis delivered as a short burst of high force.

In an embodiment, a power charge 116 is presented that opens the pathfrom the combustion gas created by the burning power charge 116 to theportions of the wellbore tool upon which a force needs to be exerted farearlier in the combustion process than in the prior art. For thewellbore tools presented in FIG. 2 and FIG. 3, this path includes thegas diverter channel 134 and the portions of the wellbore tool whereforce is exerted are the portions of the outer sleeve 120 and the innerpiston 104 forming expansion chamber 128.

FIG. 4 illustrates a cross-section of the power charge in accordancewith an embodiment. The outer dimensions of the power charge 116 may beidentical to those found in the prior art, thus permitting its use inexisting generic wellbore tools 60. The portion 180 that forms themajority of power charge 116 of FIG. 4 is a slow-burning formulation ofenergetic material, e.g., a power charge formulation with a burn-rate onthe order of about 1 ft/min to about 0.13 ft/min. A portion 182 of powercharge 116 is a relatively fast-burning energetic material. For example,the portion 182 may be pure black powder or BPS and have a burn rate onthe order of about 18 ft/min up to about 42 ft/min. Each of theslow-burning portion 180 and the fast-burning portion 182 occupy aseparate volume of the power charge 116. Further, the volume of theslow-burning portion 180 is continuous and the volume of thefast-burning portion 182 continuous, i.e., there exists one and only onevolume of each in a single power charge.

With continuing reference to FIGS. 3 and 4, and further reference toFIG. 5A, the slow-burning portion 180 volume of the power charge 116 maydefine the fast-burning portion 182 volume of the power charge 116 suchthat the fast-burning portion 182 volume is a chamber formed within theslow-burning portion 180 volume. For example, as in the exemplary powercharge(s) shown in FIGS. 3 and 4, the cylindrically shaped power charge116 may include the slow-burning portion 180 volume formed as anelongate annular member. The fast-burning portion 182 volume may be theopen inner area of the annulus, i.e., the chamber formed within theslow-burning portion 180 volume, defined and bounded by an inner annulussurface 189. The fast-burning energetic material may be filled, packed,inserted, etc. in the chamber. Alternatively, the fast-burning energeticmaterial may be formed as a core of the power charge 116 such that thefast-burning energetic material and the slow-burning energetic materialare arranged together and formed into the power charge 116 withoutdiscrete or delineated portions. The chamber, or the fast-burningportion 182 volume, generally, may extend along any length within theslow-burning portion 180 volume including all the way therethrough, ormay otherwise be formed by any technique to occupy any particularvolume, of any particular profile or configuration, consistent with thisdisclosure.

Further, in various alternative embodiments, the power charge 116 mayhave any geometry, cross-sectional profile, arrangement, and the likeincluding the incorporation and configuration of the slow-burningportion 180 volume and the fast-burning portion 182 volume consistentwith this disclosure and as particular applications may dictate.

FIG. 5A illustrates the end of the power charge 116 shown in FIG. 4designed to cause ignition portion 188 to be disposed adjacent theinitiator 118 when power charge 116 is properly inserted in power chargecavity 114, according to an embodiment. FIG. 5B is a cross-sectionalview of the power charge 116 shown in FIG. 4 showing the relationshipbetween the slow-burning portion 180 and the fast-burning portion 182.FIG. 5C is a cross-sectional view of the power charge 116 shown in FIG.4 showing a portion of thereof having only slow-burning energeticmaterial, i.e., lacking fast-burning portion 182.

Ignition of the initiator 118 adjacent ignition portion 188 willinitiate combustion of both the slow-burning portion 180 and thefast-burning portion 182 of the power charge 116 shown in FIG. 4. Thedifferent burn rates of the portion 180 and the portion 182 results incombustion of the fast-burning portion 182 occurring much more quicklythan the combustion of the portion 180. The fast and slow-burn ratesdiffering by a factor in the range of about a hundred to several hundredtimes, portion 182 will be completely consumed in the time that only asmall portion of portion 180 has been consumed. As with any energeticmaterial used in a power charge, once consumed, the volume previouslyoccupied by the energetic material is now occupied primarily by gas. Thevolume previously occupied by the energetic material becomes part of thepath for pressurized gas to access the expansion chamber 128. Thus, therelatively fast combustion of the fast-burning portion 182 quickly opensa path through the power charge 116 that would have taken substantiallylonger to open if the combustion of the slow-burning portion 180 wererelied upon to open the path. Once opened, the path for pressurized gasformerly occupied by fast-burning portion 182 causes the combustiongases and, thus, gas pressure from the combustion of slow-burningportion 180 to be conveyed past the unreacted portion of theslow-burning portion 180.

Thus, the current problem of pressure build-up being delivered as anexcessively strong single pulse to the gas divertor channel is avoidedwith the provision of a fast-burning portion 182 through some or all ofthe slow-burning portion 180. Rather, depending upon the differentcombustion rates between the slow-burning portion and fast-burningportion 182 of the power charge 116, only a relatively small pressurebuild-up will occur prior to a path being opened to the gas diverterchannel 134 or other access route to the area in the wellbore tool wheremechanical work is achieved, e.g., expansion chamber 128. In theembodiments shown in FIG. 2 and FIG. 3, the axial force exerted on outersleeve 120 will be increased relatively gradually after fast-burningportion 182 is fully consumed, thus enabling a simple and economicalmeans of achieving slow set delivery of force by setting tool 100 ontool 102.

As illustrated in FIG. 3, FIG. 4 and FIG. 5A, the power charge 116 mayfurther include an indentation 140 adjacent the initiator 118 and/orinitiator holder 138. By providing a slight offset between initiator 118and the surface of power charge 116, the indentation 140 is configuredto increase the reliability that the initiator 118 initiates thecombustion of the power charge 116. Further, indentation 140 may befilled or lined with a booster charge (not shown), the chemical makeupof the booster charge being more sensitive to initiation than thechemical makeup of either or both the fast-burning and slow-burningportions of the power charge 116.

Although the figures, particularly FIG. 4 and FIG. 5B, show thefast-burning portion 182 as approximately coaxial to the remainder ofthe power charge 116, this geometry is one option. FIG. 6 illustrates anembodiment where the fast-burning portion 182 is radially offset fromthe axis of the power charge 116. The geometry of FIG. 6 may be selectedto decrease the distance between the fast-burning portion 182 and thegas diverter channel 134 or other access route to the area in thewellbore tool where mechanical work is achieved is located. Thepossibility exists that the fast-burning portion 182 may be completelyconsumed but the reaction still needs to consume the slow-burningportion 180 to complete the path for pressurized gas to the gas diverterchannel 134. The geometry of FIG. 6 can be one solution to this issue.Another solution to this issue is to have the fast-burning portion 182approach very close to or even meet the distal end 184 of power charge116. The fast consumption of the fast-burning portion 182 relative tothe slow-burning portion 180 will, thus, result in a path through theentirety (or substantially the entirety) of the power charge 116 beforea substantial portion of the portion 180 has been consumed. For example,in an exemplary embodiment in which the slow burning portion 180

In the exemplary embodiment illustrated in FIG. 3, the single usesetting tool 100 may include a shear element 152 connected to the innerpiston 104 and the outer sleeve 120. The shear element 152 may beconfigured to prevent the axial sliding of the outer sleeve 120 relativeto the inner piston 104. The shear element 152 allows the axial slidingof the outer sleeve 120 relative to the inner piston 104 subsequent tothe formation of the combustion gas in the expansion chamber 128exceeding a threshold pressure. That is, once the gas pressure inexpansion chamber 128 reaches a threshold pressure, the force pushingaxially against outer sleeve 120 will cause failure of shear pin 152.The outer sleeve 120 will then be free to move axially relative to innerpiston 104. In the context of the power charge 116 embodiments describedherein, the force to shear the shear element 152 can be set higher thanthe greatly reduced initial force from burning of energetic materialprior to a path to the gas diverter channel 134 being opened. Thus, theshear element 152 prevents the initial gas build-up from having anyeffect on the ultimate work performed by the wellbore tool.

The exemplary single use setting tool 100 may also include a gas bleed154 positioned such that after gas pressure in the expansion chamber 128has moved the outer sleeve 120 and inner piston 104 relative to oneanother to a point where gas bleed 154 moves past a first seal assembly148, the gas bleed 154 may vent excess pressures in the expansionchamber 128 and the central bore 126 of the outer sleeve 120, throughthe body 110 of the outer sleeve 120. A second seal assembly 150 sealsthe outer sleeve 120 to the inner piston 104 such that the expansionchamber 128 is sealed on both ends and gas pressure may build uptherein.

In an embodiment, either or both the power charge 116 and the powercharge cavity 114 may have a gas pressure path formed therein before anycombustion is initiated. FIG. 7 shows a side cross-sectional detail viewof the power charge cavity 114 portion of a setting tool 100. Thesetting tool 100 of FIG. 7 includes one or more grooves 142 disposed atan intersecting surface 144 between the power charge 116 and the annularwall 112 of cavity 114. The one or more grooves 142 may extend axiallyalong a substantial portion of the intersecting surface 144. The groove142 is configured to allow gas pressure communication between theproximal, initiation end 186 of power charge 116, where combustionbegins, and the expansion chamber 128 via the gas diverter channel 134.

The groove 142 may be formed in the power charge 116 or the annular wall112 of the setting tool cavity 114. FIG. 7 shows a set of grooves 142present in the annular wall 112 of the power charge cavity 114. Astandard, cylindrical power charge 116 disposed in the power chargecavity of 114 of FIG. 7 will have a gas pressure path, in the form ofgrooves 142, linking the initiation end 186 of the power charge 116 tothe expansion chamber 128 via the gas diverter channel 134. The powercharge shown in FIG. 8 does not have a standard cylindrical shape.Rather, FIG. 8 shows a power charge 116 in which two axial grooves 142′have been formed into the outer surface thereof. The power charge 116shown in FIG. 8 inserted in the power charge cavity 114 of tool 100 willhave a gas pressure path, in the form of grooves 142′, linking theinitiation end 186 of the power charge 116 to the expansion chamber 128via the gas diverter channel 134. Grooves 142 and 142′ may also beformed in both the annular wall 112 of the power charge cavity 114 andthe power charge 116 itself.

Thus, grooves 142 and/or 142′ provide an immediate or far earlier gaspressure path from the combusting initiation end 186 of the power charge116 to the gas diverter channel 134. Like the fast-burning portion 182,the grooves 142, 142′ prevent a large build-up of gas pressure in cavity114 that is blocked from reaching gas diverter channel 134 by unburnedpower charge 116. Thus, the current problem of pressure build-up beingdelivered as a single pulse may be reduced with grooves 142, 142′.Rather, the axial force exerted on outer sleeve 120 may be increasedrelatively gradually, over the course of seconds (or any particularamount of time as applications dictate and the design of the cavity 114,the power charge 116, and the gas diverter channels 134, among otherthings, may accomplish), thus enabling a simple and economical means ofachieving slow set delivery of force in a wellbore tool.

The present disclosure, in various embodiments, configurations andaspects, includes components, methods, processes, systems and/orapparatus substantially developed as depicted and described herein,including various embodiments, sub-combinations, and subsets thereof.Those of skill in the art will understand how to make and use thepresent disclosure after understanding the present disclosure. Thepresent disclosure, in various embodiments, configurations and aspects,includes providing devices and processes in the absence of items notdepicted and/or described herein or in various embodiments,configurations, or aspects hereof, including in the absence of suchitems as may have been used in previous devices or processes, e.g., forimproving performance, achieving ease and/or reducing cost ofimplementation.

The phrases “at least one”, “one or more”, and “and/or” are open-endedexpressions that are both conjunctive and disjunctive in operation. Forexample, each of the expressions “at least one of A, B and C”, “at leastone of A, B, or C”, “one or more of A, B, and C”, “one or more of A, B,or C” and “A, B, and/or C” means A alone, B alone, C alone, A and Btogether, A and C together, B and C together, or A, B and C together.

In this specification and the claims that follow, reference will be madeto a number of terms that have the following meanings. The terms “a” (or“an”) and “the” refer to one or more of that entity, thereby includingplural referents unless the context clearly dictates otherwise. As such,the terms “a” (or “an”), “one or more” and “at least one” can be usedinterchangeably herein. Furthermore, references to “one embodiment”,“some embodiments”, “an embodiment” and the like are not intended to beinterpreted as excluding the existence of additional embodiments thatalso incorporate the recited features. Approximating language, as usedherein throughout the specification and claims, may be applied to modifyany quantitative representation that could permissibly vary withoutresulting in a change in the basic function to which it is related.Accordingly, a value modified by a term such as “about” is not to belimited to the precise value specified. In some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value. Terms such as “first,” “second,” “upper,”“lower,” etc. are used to identify one element from another, and unlessotherwise specified are not meant to refer to a particular order ornumber of elements.

As used herein, the terms “may” and “may be” indicate a possibility ofan occurrence within a set of circumstances; a possession of a specifiedproperty, characteristic or function; and/or qualify another verb byexpressing one or more of an ability, capability, or possibilityassociated with the qualified verb. Accordingly, usage of “may” and “maybe” indicates that a modified term is apparently appropriate, capable,or suitable for an indicated capacity, function, or usage, while takinginto account that in some circumstances the modified term may sometimesnot be appropriate, capable, or suitable. For example, in somecircumstances an event or capacity can be expected, while in othercircumstances the event or capacity cannot occur—this distinction iscaptured by the terms “may” and “may be.”

As used in the claims, the word “comprises” and its grammatical variantslogically also subtend and include phrases of varying and differingextent such as for example, but not limited thereto, “consistingessentially of” and “consisting of.” Where necessary, ranges have beensupplied, and those ranges are inclusive of all sub-ranges therebetween.It is to be expected that variations in these ranges will suggestthemselves to a practitioner having ordinary skill in the art and, wherenot already dedicated to the public, the appended claims should coverthose variations.

The terms “determine”, “calculate” and “compute,” and variationsthereof, as used herein, are used interchangeably and include any typeof methodology, process, mathematical operation or technique.

The foregoing discussion of the present disclosure has been presentedfor purposes of illustration and description. The foregoing is notintended to limit the present disclosure to the form or forms disclosedherein. In the foregoing Detailed Description for example, variousfeatures of the present disclosure are grouped together in one or moreembodiments, configurations, or aspects for the purpose of streamliningthe disclosure. The features of the embodiments, configurations, oraspects of the present disclosure may be combined in alternateembodiments, configurations, or aspects other than those discussedabove. This method of disclosure is not to be interpreted as reflectingan intention that the present disclosure requires more features than areexpressly recited in each claim. Rather, as the following claimsreflect, the claimed features lie in less than all features of a singleforegoing disclosed embodiment, configuration, or aspect. Thus, thefollowing claims are hereby incorporated into this Detailed Description,with each claim standing on its own as a separate embodiment of thepresent disclosure.

Advances in science and technology may make variations and substitutionspossible that are not now contemplated by reason of the imprecision oflanguage; these variations should be covered by the appended claims.This written description uses examples to disclose the method, machineand computer-readable medium, including the best mode, and also toenable any person of ordinary skill in the art to practice these,including making and using any devices or systems and performing anyincorporated methods. The patentable scope thereof is defined by theclaims, and may include other examples that occur to those of ordinaryskill in the art. Such other examples are intended to be within thescope of the claims if they have structural elements that do not differfrom the literal language of the claims, or if they include structuralelements with insubstantial differences from the literal language of theclaims.

What is claimed is:
 1. A power charge for actuating a wellbore tool, thepower charge comprising: a first end and a second end opposite the firstend; an outer surface extending from the first end to the second end; agroove formed in the outer surface; a first volume comprising a firstenergetic material; and a second volume comprising a second energeticmaterial, wherein the second energetic material is a faster burningmaterial compared to the first energetic material.
 2. The power chargeof claim 1, wherein the second volume extends from a position adjacentthe first end towards the second end.
 3. The power charge of claim 1,wherein the second volume extends from a position adjacent the first endto a position adjacent the second end.
 4. The power charge of claim 3,wherein the second volume extends all the way through the power chargefrom the first end to the second end.
 5. The power charge of claim 1,wherein the second volume is coaxial with the first volume.
 6. The powercharge of claim 1, further comprising an indentation in the power chargeadjacent the first end.
 7. The power charge of claim 6, furthercomprising a booster positioned within the indentation.
 8. The powercharge of claim 6, wherein the second volume extends from a positionadjacent the indentation, in a direction away from the indentation. 9.The power charge of claim 1, further comprising a path formed within thefirst energetic material for directing pressurized gas out of the powercharge, wherein the second energetic material fills at least a portionof the path.
 10. A wellbore tool including a power charge for actuatingthe wellbore tool, comprising: a tool body wall defining a power chargecavity, wherein the power charge is positioned within the power chargecavity and the power charge includes: a first end and a second endopposite the first end, an outer surface extending from the first end tothe second end, a groove formed in the outer surface, a first volumecomprising a first energetic material, and a second volume comprising asecond energetic material that is a faster burning material compared tothe first energetic material.
 11. The wellbore tool of claim 10, furthercomprising an initiator holder positioned within the power charge cavityand configured for receiving and positioning an initiator adjacent tothe power charge within the power charge cavity, wherein the initiatorholder is configured for positioning an initiating output portion of theinitiator adjacent to an ignition portion of the power charge.
 12. Thewellbore tool of claim 11, wherein the ignition portion of the powercharge includes the first energetic material or the second energeticmaterial.
 13. The wellbore tool of claim 12, wherein the ignitionportion of the power charge includes the second energetic material andthe initiator holder is configured for positioning the initiating outputportion of the initiator adjacent to the second volume.
 14. The wellboretool of claim 11, wherein the power charge further includes anindentation in the power charge and a booster positioned within theindentation, wherein the initiator holder is configured for positioningthe initiating output portion of the initiator adjacent to the booster.15. The wellbore tool of claim 10, further comprising a channel open toand extending, through the tool body wall, from the power charge cavityto an outside of the tool body wall.
 16. The wellbore tool of claim 15,wherein the groove defines a gas pressure path between the tool bodywall and the power charge, within the power charge cavity, and the gaspressure path is open to the channel.
 17. The wellbore tool of claim 10,further comprising a path formed within the first energetic material fordirecting pressurized gas out of the power charge, wherein the secondenergetic material fills at least a portion of the path.
 18. A methodfor actuating a wellbore tool with a power charge, comprising: providingthe wellbore tool including a power charge cavity defined by a tool bodywall of the wellbore tool; inserting the power charge into the powercharge cavity, wherein the power charge includes a first end and asecond end opposite the first end, an outer surface extending from thefirst end to the second end, a groove formed in the outer surface,wherein the groove is configured for defining a gas pressure pathbetween the tool body wall and the power charge, within the power chargecavity, when the power charge is inserted into the power charge cavity,a first volume comprising a first energetic material, and a secondvolume comprising a second energetic material that is a faster burningmaterial compared to the first energetic material; and coupling aninitiator to the wellbore tool, wherein the initiator is configured forinitiating an ignition portion of the power charge and thereby causingcombustion of the first energetic material and the second energeticmaterial and generation of gas pressure from combustion of the firstenergetic material and the second energetic material, wherein the gaspressure travels along the gas pressure path and actuates the wellboretool.
 19. The method of claim 18, wherein the tool body wall includes achannel open to and extending through the tool body wall, from the powercharge cavity to an actuation chamber of the wellbore tool, and the gaspressure builds up in the actuation chamber to actuate the wellboretool.
 20. The method of claim 19, wherein the gas pressure path is opento the channel.